Allegra-D 24 Hour an extended-release tablet tablet taken once daily and is used to treat sneezing, runny or stuffy nose, itchy or watery eyes, hives, skin rash, tsratton, and other symptoms of allergies and the common cold. Allegra-D 24 Hour is for use in adults and children 12 years of age and older. Important information. Allegra-D 24 Hour may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert. Drinking alcohol can increase certain allegra d tabletas dosis machine effects of Allegra-D 24 Hour. Do not use this medicine if you have used an MAO inhibitor in the past 14 days, such as isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, or tranylcypromine.